This invention relates to a solar photovoltaic power generation device which is for converting sun's radiation into electric power. Such a solar photovoltaic power generation device is particularly useful in a power source to be loaded on a spacecraft.
Such a solar photovoltaic power generation device is disclosed in Japanese Unexamined Patent Publication Tokkai Sho 56-2676, namely, 2676/1981 and Japanese Unexamined Patent Publication Tokkai Sho 60-180440, namely, 180440/1985. The solar photovoltaic power generation device has a predetermined generation capacity defined by a maximum electric power in order to supply the electric power to various circuit devices which are installed on the spacecraft. Generally speaking, the solar photovoltaic power generation device comprises a solar cell array wherein a plurality of power generation units are parallely arranged on a circuit board. Each of the plurality of power generation units comprises a plurality of generation elements. In general, the plurality of power generation units are electrically connected in parallel and outputs the maximum electric power. Outputs of the plurality of power generation units are supplied to a DC (direct current) converter through a shunt resistor. The output is rectified and boosted by the DC converter and then supplied to the various circuit devices.
The electric power required by the various circuit devices varies with the passage of time. This means that dump power occurs in the solar cell array when the required electric power is less than the maximum electric power. In this event, the dump power must be radiated out of the spacecraft. The shunt resistor is used for radiating the dump power. Namely, the dump power is consumed by the shunt resistor and is converted into thermal energy. The thermal energy is radiated out of the spacecraft through a radiating plate connected to the shunt resistor.
Such a solar photovoltaic power generation device has, however, a degraded utilization factor of the solar cell array. Moreover, the spacecraft is influenced by the thermal energy radiated from the radiating plate. The spacecraft has increased bulk and increased weight caused by the shunt resistor and the radiating plate.
In the meanwhile, the spacecraft is influenced by various disturbances, such as the planetary magnetic field, and therefore changes in attitude. The spacecraft is therefore required to perform attitude control. The attitude control is realized by means, such as a gas jet system. However, the gas jet system requires propellant in order to carry out the attitude controll This means that the spacecraft further increases in bulk and weight.